This proposal requests funding for the acquisition of a state-of-the-art high resolution transmission electron microscope and accessory equipment. The specific equipment sought includes: 1) a JEOL JEM 1200EX transmission electron microscope, 2) a SRH-10 tilting-rotating specimen holder, and 3) a Brimrose image intensifier. Each of these items is necessary for the successful implementation and completion of several ongoing N.I.H. supported projects which are briefly described within this application. While current equipment housed within the Laboratory for Ultrastructural Research and in other E.M. labs on this Campus is adequate for many routine morphological applications, investigations which demand state-of-the-art technological innovations, such as microprocessor controlled instrumental operating parameters, eucentric tilting capabilities, dry pumping systems, and/or minimum dose specimen observation, are simply not possible with existing instruments. Furthermore, the ages of the transmission microscopes presently in use on this Campus (all well over ten years old) make instrument dependability and serviceability a major factor to be considered in the formulation and successful execution of any serious research effort. The acquisition of a high resolution TEM containing the innovative technological features required by the included proposals would greatly enhance the ability of these investigators to pursue and successfully complete their research programs.